It is commonplace for goods suppliers to stack goods on pallets which are then transported to end users or intermediaries in the supply chain such as retailers and wholesalers. Typically the goods are held in place on the pallets by being wrapped with several layers of plastic stretch film which must, at some stage, be removed to provide access to the goods on the pallet. Machinery for automatically wrapping goods on pallets with plastic stretch film is known. Such machines typically comprise a rotary turntable on which a pallet stacked with goods is placed for rotation during a wrapping process. A vertical column positioned adjacent the turntable supports a roll of packaging plastic stretch film with its axis generally vertical whereby the film can be drawn from the roll and onto the goods on the pallet as the turntable is rotated. The support structure for the plastic film roll is driven upwardly/downwardly to sequentially lay overlapping layers of film web on the goods on the pallet. At the end of this process, the film in some machines is gripped by a pair of gripping jaws and is then cut by a suitable mechanism including hot wire cutting mechanisms with the cut wrapped film being pressed and adhered to the film covering the goods on the pallet. The film extending from the roll remains held by the gripping jaws until the wrapping process is recommenced with a new pallet.
Fully automated pallet wrapping machines of the aforementioned kind are often driven by pneumatic actuators which require a compressed air supply system. Normally this is supplied beneath the rotatable turntable but necessarily requires the turntable load carrying surface to be relatively elevated to fit the pneumatic air supply equipment thereunder. This then requires conveyor systems to load stacked pallets on the turntable or, alternatively, the use of mechanized lift trucks. There are, however, many businesses that have the need for wrapping loaded pallets but which do not have any compressed air supply nor do they have the space or the desire to have fully automated wrapping machines.
U.S. Pat. No. 4,216,640 discloses a pallet wrapping machine of the aforementioned type. In this disclosure, a pair of film gripping arms are carried on the rotatable turntable and are raised from an opposed position approximately parallel to the turntable supporting surface to an elevated film gripping position by means of pneumatic actuators. One of the gripping arms is provided with an electrical resistance wire acting as a cutting means to separate the film wrapped from remaining film on the film supply roll. The last layer of film is laid onto the wrapped goods on the pallet with the lower edge of the film web positioned adjacent the top surface of the pallet. The confronting gripping zones of the gripping arms, in the elevated gripping position also grip the film web from a position adjacent the top surface of the pallet to fully grip the width of the film web.
Canadian patent specification no. 1215910 also discloses a pallet wrapping machine generally of the aforementioned type but intended for use with a web that is not treated for self adherence to itself. The disclosed machine includes a mechanism for forming the wrapping web into a rope after leaving the supply roll and the machinery further includes clamping means for holding the rope formed web material, cutting means for cutting the rope formed web material and securing means such as a stapler for securing the roped formed web material to a previously laid layer of web material.
It is becoming more common for receivers of goods wrapped on pallets n the aforementioned manner to provide automated or semi automated inward handling machines to minimise manual labour required. It has been found that the tail end of the wrapped plastic film web may detach from the wrapped film web surrounding the goods stacked on the pallet. There are a variety of reasons for this including the structure of certain pallet wrapping machines, environmental conditions and the stored energy in the stretched plastic stretch film itself. However, if this does occur with the tail end hanging down below the pallet itself, automated inward handling machines are often caused to malfunction or not function defeating any advantages provided by such machinery. In such circumstances the detached film tail ends might need to be reattached manually by any suitable means or the packed pallet might simply be returned to the supplier at the suppliers cost.
The preferred aim of the present invention is to provide improvements in pallet wrapping machines or parts thereof that will enable the use of automated inward handling machinery with pallets wrapped by such machines.
A further preferred aim of the present invention is to provide apparatus that might be retrofitted to existing pallet wrapping machinery that will overcome or minimise the problem of detached film web tail ends.
A still further preferred aim of the present invention is to provide pallet film wrapping machinery that might be operated using conventional electric power without requiring compressed air actuating machines.